This invention relates generally to injection molding nozzles and more particularly to a nozzle with an improved removable gate insert member.
Injection molding nozzles having a removable gate insert are known in the art. The applicant's U.S. Pat. No. 4,286,941 entitled "Injection Molding Nozzle Seal" which issued Sept. 1, 1981 shows an early example of a nozzle seal with one end seated in the forward end of a nozzle and the other end extending into an opening in the cavity plate to the cavity. More recently, the applicant's Canadian patent applications Ser. No. 532,677 filed March 20, 1987 entitled "Injection Molding Nozzle and Method" and 549,516 filed October 16, 1987 entitled "Injection Molding System having Clamped Rotatable Nozzles and Method" show a removable tip or gate insert member. While these previous gate inserts do increase heat flow to the gate area, this has been found to still not be sufficient for some materials such as crystaline materials having a narrow temperature window.
It is also known to provide increased heat in the gate area using a probe with a heated tip which the melt flows around such as shown in U.S. Pat. No. 4,643,664 to Yoshida which issued Feb. 17, 1987. A nozzle having a heated pointed tip is shown in the applicant's Canadian patent application Ser. No. 49,518 filed Oct. 16, 1987 entitled "Injection Molding Nozzle having Grounded Heating Element Brazed into Pointed Tip" However, none of the prior art shows a removable gate insert which the melt flows through and which provides sufficient heat for these temperature critical applications.